<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>css三角原理</title>
    <style>
        .tty {
            width: 0;
            height: 0;
            line-height: 0;
            font-size: 0;
            border: 10px solid transparent;
            border-bottom-color: #000;
        }

        .ttt {
            width: 0;
            height: 0;
            line-height: 0;
            font-size: 0;
            border: 50px solid #000;

        }
    </style>

</head>

<body>
    <div>
        <div class="tty"></div>
        <div class="ttt"></div>
    </div>
</body>

</html>